1. Field of the Invention
This invention relates to a powered jacking leg that forms part of the landing gear for articulated trailers.
2. Description of Related Art
For many years articulated trailers have included manually operable jacking legs located at the forward end of the trailer. The manual raising or lowering of jacking legs is an onerous task requiring a significant degree of strength. Current laws relating to health and safety are raising serious questions about the potential hazards of manually operating the jacking legs of trailers.
There have been a number of proposals to automate the raising and lowering of the legs of trailers. One solution to this problem is suggested in our earlier patent application WO 00/51859. This application relates to a demountable system that could be attached to existing jacking leg structures to provide a powered drive through the use of an electric motor. Most jacking systems incorporate a gearbox that facilitates a speed change so that when the forces are low the leg can be moved at high speed but when a heavy load has to be lifted, the ratios can be substantially reduced to render the task easier.
A problem with the use of the existing speed change systems is that the speed change mechanism is cumbersome and at times difficult to operate. When the leg is under load it is very difficult to move the gear wheels from one position to another. Thus, the demountable powered systems tend to be bulky and at times difficult to operate.
It is these issues that have brought about the present invention.